Resistance to Extinction After Gradually Increased or Decreased Ratio of Partial Reward Schedule

Abstract

Resistance to extinction of the gradually increased (gI) or decreased (gD) ratio of partial reinforcement has been investigated in order to assess effectively partial-reinforcement theories. COGAN et al. (1975) reported greater resistance in gD than in gI employing an extensive acquisition training and the sucrose solution as a reinforcer, and interpreted the results as supporting AMSEL'S frustration hypothesis. ISHIDA (1978), however, found the opposite result with food reward after a moderate number of acquisition trials. Thus, the present study was desingned to determine the resistance to extinction after gI and gD schedules under appropriately arranged experimental conditions, and to assess partial-reinfocement hypotheses.Three groups of 9 rats each were trained with extensive acquisition trials (12 trials a day for 9 days) and then extinguished (12 trials a day for 6 days) in a straight alley. Groups gI and gD received the reward sequences as shown in Table 1. Group RA, which was added as a control, received random sequence. All three groups were rewarded at 53% with food pellets.There was not a significant difference among groups during acquisition, although performance of gI was below those of the other two groups in early trials (Fig. 1). During extinction three groups differed significantly, i. e., group gI was most resistant to extinction, RA was less, and gD was least (Fig. 2).The extinction results did not support the AMSEL'S view that the later occuring nonreinforcements (the group of gD) should produce greater frustration and greatest resistance to extinction. The present findings are interpreted both by reinforcement-level view (CAPALDI, 1978) and attention theory (SUTHERLAND and MACKINTOSH, 1971). However, it is suggested that CAPALDI'S thesis is more appropriate one, considering the predictability of the results, especially the difference between RA and each of gI and gD.